All national building codes specify refractory mortar conforming to ASTM C-199 for installing firebrick and clay flue linings in masonry fireplaces and chimneys.

Easy to use, economical and versatile, HEAT STOP® resists temperatures well above 2000° F, assuring code compliance and a quality installation. Regular cement or mortar found in most mortar mixes resists temperatures up to 600-800° F, but residential installations operate well in excess of 800° F.